An inter-vehicle distance control apparatus has been proposed in, for example, Japanese Patent No. 2567548. The inter-vehicle distance control apparatus controls a speed of a subject vehicle based on a relative-velocity between the subject vehicle and a preceding vehicle to maintain an inter-vehicle distance between the subject and preceding vehicles at a target inter-vehicle distance. According to the inter-vehicle distance control apparatus, when the speed of the subject vehicle is fast and when the inter-vehicle distance is small, a time constant associated with a filter for outputting a relative-velocity is decreased. When the speed of the subject vehicle is slow and when the inter-vehicle distance is large, the time constant associated with a filter for outputting the relative-velocity is increased. The above manners may improve a capability of controlling the inter-vehicle distance in respects of response and stability.
However, since conventional inter-vehicle distance control apparatuses control a speed of a subject vehicle based on a relative-velocity between the subject vehicle and a preceding vehicle to maintain an inter-vehicle distance at a target inter-vehicle distance, a resultant acceleration may provide uncomfortable acceleration feeling to a driver of the subject vehicle.